In military applications, 2,4,6-trichloroaniline (TCA) is utilized for the preparation of insensitive energetic material (TATB) that is employed in several Navy weapons systems. Currently, TCA is not manufactured domestically; most likely due to the hazards of using chlorine gas. The synthesis of 2,4,6-trichloroaniline has almost invariably been accomplished by chlorination of aniline with chlorine or sulfuryl chloride. (Muathen, H. A. Helv. Chim. Acta. 2003, 86, 164-168; Hofmann, A. W. Ann. 1845, 53, 1-57; Meyer, V.; Sudborough, J. J. Ber. 1894, 27, 3146-3153; Sudborough, J. J. J. Chem. Soc. 1894, 65, 1028-1031; Chattaway, F. D.; Irving, H. J. Chem. Soc. 1933, 142-143; Orloff, H. D.; Napolitano, J. P. U.S. Pat. No. 2,675,409, Apr. 13, 1954; Werner, F.; Roxo, B.; Mannes, K.; Trescher, V. U.S. Pat. No. 4,447,647, May 8, 1984; Kim, C.-U.; Jin, H.-J.; Lee, S.-B.; Lee, J.-M. Hwahak Konghak. 1990, 28, 230-236. Q4; Mehilal.; Salunke, R. B.; Agrawal, J. P. Indian J. Chem., Sect. B. 2002, 41, 604-607; Wenghoffer, L. J. Prakt. Chem. 1877, 16, 448-466; Eller, W.; Klemm, L. Ber. 1922, 55, 217-224.) Although the latter reactions typically provide TCA in high yield, these reagents require special handling because of their highly corrosive nature. In addition, chlorine and, especially, sulfur dioxide emissions must be strictly controlled. (U.S. Clean Air Act. Public Law 101-549, 1990.)
The synthesis of TCA by means other than chlorine gas are few (Muathen, H. A. Helv. Chim. Acta. 2003, 86, 164-168). Chlorine gas is highly toxic and difficult to work with owing to its highly corrosive nature. Domestic manufacture of has ceased probably on account of these problems. There exists a need in the art for procedures that are safer and use less toxic N-chloro reagents to make TCA.
More convenient reagents for aromatic chlorinations are N-chloro reagents including, but not limited to, N-chlorosuccinimide (NCS). The chlorination of aniline and substituted anilines with N-chloro reagents, including NCS, has been studied. (Chao, T. H.; Cipriani, L. P. J. Org. Chem. 1961, 26, 1079-1081; Searle, N. E.; Cupery, H. E. J. Org. Chem. 1954, 19, 1622-1627; Neale, R. S.; Schepers, R. G.; Walsh, M. R. J. Org. Chem. 1964, 29, 3390-3393.) The main concern of these studies was determining the ortho-para regioselectivity of monochlorination. Other literature reports showed that 4-bromoaniline and 3,5-difluoro-4-iodoaniline undergo dichlorination at the 2,6-position in chloroform with NCS or N-chloro-2,4-dichloroacetanilide. (Reed, W. W.; Orton, K. J. P. J. Chem. Soc. 1907, 91, 1543-1554; Manka, J. T.; Kaszynski, P. J. Flourine Chem. 2003, 124, 39-43.) Previously, there was no reported instance of the study of tri-chlorination of an aniline using N-chloro reagents.
It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not to be viewed as being restrictive of the invention, as claimed. Further advantages of this invention will be apparent after a review of the following detailed description of the disclosed embodiments, which are illustrated schematically in the accompanying drawings and in the appended claims.